Discrimination indices in the school-achievement test. Difference between average scores.
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Achievement↗
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Discrimination indices in the school-achievement test. Difference between score distributions.
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Achievement↗
EEG as a cross species indicator of neurotoxicity.
The electroencephalogram (EEG) is a promising measure in the field of neurotoxicology. It can be well quantified by techniques which can be interpreted both physically and statistically although not necessarily physiologically. Such quantification schemes are briefly discussed in this paper. However, the quantification of EEG is not trivial in either the mathematical or computational sense. The relationship of EEG to brain function or brain pathology is not very well understood by some standards, perhaps due to poor quantitative methods or erroneous assumptions about brain-behavior relationships. EEG has a similar appearance across species. Hence the measure has great promise as a cross-species indicator of neurotoxicity. Not many quantitatively sound neurotoxicological studies using EEG have been published. It must be strongly emphasized that (a) more methods development is needed before the promise of cross species generality can be realized and (b) naive and/or half-hearted attempts to use this measure are perilous.
Animals↗
[Hemodynamic characteristics in different models of experimental hypokinesia].
The effect of hypokinesia on systemic hemodynamics has been investigated in rat and rabbit experiments using dispersion analysis. It has been shown that different models of hypokinesia produce hemodynamic disorders which depend on the type and duration of hypokinesia and animal responses to them. In rats the exposure to hypokinesia causes the hypertensive symptom-complex while in rabbits hypotensive disorders. The application of the dispersion analysis allows quantitative estimation of the hypokinetic effect on demonstrative indexes and detection of the most vulnerable parameter.
Animals↗
Evaluating multiple diagnostic tests with partial verification.
To evaluate diagnostic tests, one would ideally like to verify, for example, with a biopsy, the disease state of all subjects in a study. Often, however, no all subjects are verified. Previous methods for evaluation assume that the decision to verify depends only on recorded variables. Sometimes, particularly if the disease process is not well understood, the decision to verify may also depend on unrecorded variables related to disease. We propose a method to estimate the true- and false-positive rates of multiple tests while adjusting for the effect, on the decision to verify, of unrecorded variables related to disease. To put the estimates into a more usable form, we develop a simple algorithm for creating a receiver-operating curve which maximizes the true-positive rate, given the false-positive rate. We apply the methodology to data on the early detection of prostate cancer using ultrasonography, digital rectal exam, and prostate specific antigen.
Biometry↗
A critical band filter in touch.
Separate mechanoreceptor systems in humans were isolated by varying the spectra of vibrotactile stimuli. First, the function relating threshold to frequency of a sinusoid was obtained on the fingertip for each of four subjects, and it was found to comprise two limbs: a Pacinian and a non-Pacinian limb. The peak sensitivity within the Pacinian limb (mediated by Pacinian corpuscles) was around 250 Hz and spanned the region from 65 to 400 Hz. The non-Pacinian limb showed no detectable change in sensitivity in the region between 10 and 65 Hz. These two limbs were then treated as psychophysical channels in experiments in which narrow band noise and individual sinusoids were used to excite one or both channels. In the second and third experiments, the noise stimuli varied in bandwidth from 8 to 70 Hz and varied in center frequency from 25 to 218 Hz. Masking functions were obtained for ON-frequency conditions (the sinusoidal test and noise masker occupied the same frequency region) and for OFF-frequency conditions (the test and masker occupied different frequency regions). The ON-frequency experiments were used to estimate the signal-to-noise ratio (S/N) of the Pacinian channel at threshold. The OFF-frequency masking experiments were used to infer the shape of the Pacinian channel at frequencies below 65 Hz, where thresholds for Pacinian activation were above detection threshold. The results of these three experiments predicted the findings of a fourth masking experiment with a parameter free model that treated the Pacinian channel as a filter that integrates stimulus power. The results show that the Pacinian channel is analogous to a critical band in the auditory system.
Acoustic Stimulation↗
Prediction of decompression illness using bubble models.
The method of maximum likelihood was applied to models of bubble formation and evolution against data involving decompression illness (DCI). Equilibrium and non-equilibrium gas kinetic models were tested under the constraint of a finite tissue volume. The equilibrium model (leq), where the internal gas of a bubble is in partial pressure and mechanical equilibrium with the gas dissolved in tissue, assumed formation of a bubble upon any gas supersaturation. The non-equilibrium model (neq), where mechanical equilibrium is maintained but the exchange of gas between the bubble and the tissue is governed by a rate constant, assumed formation of a bubble at the metastable equilibrium state which requires a specific degree of gas supersaturation. In addition, another version of bubble evolution based on the diffusivity of gas in tissue (vl) was tested under similar finite volume constraints. Model parameters included liquid surface tension, the gas exchange rate constant, gas solubility, and the tissue time constant. The risk of DCI was based on the bubble radius (R) raised to powers ranging from 0 to 6. The data included 2,023 man-dives in 630 different dive profiles of air and nitrox gas mixtures with depth ranging from 1.75 to 7.09 bar and bottom time ranging from 2.8 to 300.2 min. There were 97 occurrences of DCI and 27 occurrences of marginal symptoms. Predictions of the neq and vl models were quite similar and suggested that the tissue primarily responsible for bubble formation leading to DCI in the present analysis has a perfusion rate of about 4.0 ml blood.100 ml-1.min-1. The best fit of the data for a single compartment of 10(-4) ml vol was obtained with the leq model and a risk based on R4, and an estimated time constant of 95.6 +/- 9.8 min.
Decompression Sickness↗
Does Aerua lanata have diuretic properties?
We have compared the diuretic activity of 200 ml of sucrose flavoured aqueous extract of the herb Aerua lanata with that of 200 ml sucrose flavoured weak infusion of tea leaves, and 200 ml of water, in 14 healthy volunteers under standardized conditions. Each volunteer acted as his or her own control in the three protocols, and chemical, physical and statistical analyses were performed "blind" by coding all urine and blood samples collected. A. lanata extract did not significantly increase urine flow, sodium excretion, potassium excretion, or urine and plasma osmolality as compared to an infusion of tea or plain water.
Adult↗
[The stress-protective effect of fenazepam in rats with different capacities for escape in an acute aversive situation].
Stress-protective effect of phenazepam (1 mg/kg) was studied in rats with different ability to avoid acute aversive situation. Two types of extreme situations were created, immobilization and hyperkinesia (permanent running inside the wheel). It was found out that rats which easily avoided acute aversive situation (I group) were more resistant to extreme effects. In immobilization stress phenazepam produced protective effect mostly in rats with low ability to avoid acute stress situation (II group). In situation with hyperkinesia the drug did not essentially influence the state of rats of the II group and even aggravated the state of rats of the I group. It seems likely that stress resistance of animals and dissimilar protective effects of phenazepam are determined by distinctions in coping mechanisms.
Acute Disease↗
[The dependence of striatal control over the temporal organization of behavior on the function of beta-adrenergic mechanisms].
Bilateral striatectomy disorganized the rhythmical structure of forced swimming and circadian motility of rats. Destruction of dorsal but not ventral striatum eliminated the effect of beta-adrenoblocker propranolol on temporal organization of behaviour. The results suggest that just the dorsal striatum is mainly subjected to adrenergic control.
Adrenergic beta-Antagonists↗
[The neurochemical characteristics of rats differing by their behavior in the emotional resonance test. Free-radical processes and lipids of the cerebral cortex in older rats].
Free radical processes and lipid content in brain membranes were investigated in old male Wistar rats with differences in individual behaviour in "emotional resonance" test. Two groups of rats were selected, i.e. 1--which stayed for more than 2/3 of the total test time in the dark part of the experimental chamber and 2--which spent the total test time in the light part of the chamber. Free radical processes and lipid content in the cortex of the left and right brain hemispheres did not differ in control animals of groups 1 and 2. Acute immobilization stress induced changes of the studied parameters depending on behavioural type. Rats of group 2 were more reactive than those of group 1.
Acute Disease↗
[Corticosteroids limit the decrease in blood flow velocity in the microvessels of the gastric submucosal layer during stress in rats].
To evaluate the influence of stress and corticosteroids on blood flow velocity in gastric submucosal microvessels it was used intravital microfilming by means of a dark-field contact epiobjective. The plasma filled "gap" in the continuous erythrocyte flow were used as the markers to measure linear blood flow velocity. In unstressed rats the linear blood flow velocity was equal to 2.0 +/- 0.08 mm/sec (156 microvessels, 6.4 +/- 0.14 micron in diameter), calculated volume blood flow--(6.9 +/- 0.48) x 10(-5) microliters/sec. Stress (water immersion and restraint) led to a decrease of blood flow velocity in microvessels to more than double. A stress-induced decrease of blood flow velocity was more greater in rats with insufficient corticosteroid production. The linear velocity of blood flow of these rats was lowered to 0.6 +/- 0.06 mm/sec, volume blood flow to (1.6 +/- 0.21) x 10(-5) microliters/sec. Replacement corticosterone therapy increased the blood flow velocity. It was concluded that stress decreases blood flow in microvessels of gastric submucosa. The results revealed that glucocorticoids take part in normalization of blood flow of gastric microvessels during stress and this action can provide antiulcerogenic effect of corticosteroids which was shown by us previously.
Adrenal Cortex Hormones↗
[The effect of stress and corticosteroids on the rate of blood flow in the microvessels of the gastric muscular coat of rats].
In order to evaluate the influence of stress and corticosteroids on blood flow velocity in microvessels of muscular coat of the stomach we applied intravital microfilming by means of a dark-field contact epiobjective. The plasma filled "gap" in the continuous erythrocyte flow were used as the markers to measure linear flow velocity. In unstressed rats the velocity was equal to 1.76 +/- 0.07 mm/sec (182 microvessels, 3.7-8.7 mu in diameter). Stress (water immersion and restraint) led to a decrease of blood flow velocity in microvessels to more than double. A stress-induced decrease of blood flow velocity was greater in rats with insufficient corticosteroid production. The velocity of blood flow in these rats was lowered to 0.62 +/- 0.04 mm/sec. Replacement corticosterone therapy increased the blood flow velocity. It was concluded that stress decreases blood flow in microvessels of muscular coat of the stomach as well as in microvessels of mucosa. The results revealed that glycocorticoids take part in normalisation of blood flow of gastric microvessels during stress.
Adrenal Cortex Hormones↗
Use of statistical models to evaluate racing performance in thoroughbreds.
OBJECTIVE: To develop a statistical model to evaluate the influence of specific parameters on racing performance in Thoroughbreds. DESIGN: Survey. SAMPLE POPULATION: Racing records of Thoroughbreds performing in Louisiana from 1981 to 1985. PROCEDURE: Race results for 20 randomly selected days from 5 racetracks during 5 years were analyzed, using regression analysis. RESULTS: The most influential parameter was distance raced. There were significant differences in racing performance among horses at different tracks. At the tracks examined, fast racing surfaces resulted in significantly faster finish times than good racing surfaces, and good racing surfaces resulted in significantly faster finish times than muddy racing surfaces. Finish times also were significantly faster as a function of increasing purse amount and age of horse. Finish times were significantly faster during quarter 4 (summer) and significantly slower during quarter 1 (fall). Races were run at significantly faster times as the number of the race progressed during the day. The finish times were significantly slower as the number of horses competing in the race increased, as the weight carried by the horse increased, and as the starting position away from the rail increased. CLINICAL IMPLICATIONS: The coefficients used in the statistical model of this report may be used by researchers to compare before injury and after treatment finish times. The coefficients can be used to standardize past racing performances to uniform conditions, thus permitting comparison from 1 race to another to determine success of treatments and to inform owners of prognosis.
Animals↗
Test for linear trend in 2 x K ordered tables with open-ended categories.
A method of evaluating trend (positive or negative) in 2 x K ordered tables is suggested for cases in which the scores for the first (K-1) categories are known a priori but the score for the last category is not known. Such a category is termed as open-ended category in this paper. Ordered tables with an open-ended category are often encountered while evaluating the Cochran-Armitage-Mantel (CAM) trend. In the present paper, the distribution of the test statistic is presented and simulations are carried out to check the asymptotics. The method is then exemplified by an existing data set.
Biometry↗
[The chronobiological aspects of the hemodynamic effects of clonidine in Wistar rats under immobilization stress].
Radiotelemetric monitoring of hemodynamic parameters was conducted in Wistar rats to study the chronobiological dependence of the effect of clonidine on changes in arterial pressure (AP) and heart rate (HR) induced by immobilization stress. Clonidine injection (20 mg/kg intraperitoneally) caused significant decrease in AD at night both at rest and under stress, whereas at day time its hypotensive effect was manifested only in case of immobilization. The negative cardiochronotropic effect of clonidine was also time-dependent. Thus, chronobiological dependence of the clonidine effects at rest and under stress was disclosed.
Analysis of Variance↗
[A case-control study of prostate cancer].
In America and many European countries, prostate cancer is the most common cancer and the second leading cause of cancer death in men. Among 10-30% of all the men older than 50 years of age, a silent microscopic form of prostate cancer may be harbored. This high rate is similar throughout the world. However, few epidemiologic studies of prostate cancer have implicated its risk factors. A 1:1 matched case-control study looked into risk factors of prostate cancer. A total number of 102 cases of prostate cancer and 102 controls were surveyed. The results showed that high body mass index, history of urinary diseases, coitus frequency > 3 times per week, hormone drug use, and number of children > 3 are identified as risk factors of prostate cancer statistically, but physical labor, exercise, and age of first nocturnal emission > 18 are protective factors of prostate cancer.
Body Mass Index↗
Estimation of test sensitivity and specificity when disease confirmation is limited to positive results.
Estimation of sensitivity and specificity for diagnostic or screening tests usually requires independent confirmation of subjects as diseased or nondiseased using a gold standard. In practice, however, application of the confirmatory procedure is usually limited to individuals with one or more positive test results. For situations in which two initial tests are applied, recent literature has shown that one can use the data from confirmed disease cases to estimate the ratio of test sensitivities and the information from confirmed noncases to estimate the ratio of false-positive rates. In this paper, I show that estimates of sensitivity and specificity can be obtained for each test separately, together with an estimate of the disease prevalence. The only additional information required compared with previous methodology is the total number of individuals tested, a quantity that is usually readily available. The assumption that the test errors are independent is required. Although specific patterns of test errors cannot be identified, the overall assumption can be tested using goodness of fit. I illustrate the methods using data on breast cancer screening. Provision of sensitivity and specificity estimates for each test separately provide considerably greater insight into the data than previous methods.
Breast Neoplasms↗